This invention relates to a package system and container apparatus and a method of shipping exothermic materials.
Many chemical compositions and formulations are packaged, stored and shipped to customers in various manners and modes of transportation. Some of these products involve materials which are exothermic and can react and liberate significant amounts of heat when they reach temperatures at or above ambient or room temperature. One product group of this type is premixed chemical formulations used in electronic and aerospace adhesive applications. These formulations are typically highly reactive epoxies consisting of a resin and hardener which are combined together at the point of manufacture and sold in syringes or other sample containers as a single homogeneous material. These materials can react rapidly if they reach their reaction initiation temperature and liberate a significant amount of heat. In order to prevent premature reaction and curing, the materials are cooled to very low temperatures which greatly slow or completely suppress the polymerization reaction. These premixed and frozen formulations can be safely stored in a freezer or other suitable temperature controlled device without the risk of liberating heat. When the formulations are needed, they can be removed from cold storage and allowed to warm to room temperature where they can be applied and allowed to react. This form of product is often desired by customers since they simply have to thaw and use it, as opposed to having to mix chemicals at their manufacturing facility.
The main problem with premixed and frozen exothermic materials, as described above, is that they are extremely difficult and potentially dangerous to store for extended periods of time outside a freezer. Furthermore, they are difficult to ship using conventional means (e.g., standard non-refrigerated trucks, airplanes etc.). Because they have the potential of liberating significant amounts of heat if they reach a certain ambient temperature, they must be packed in some cooling or other medium, such as dry ice, to keep the temperature below that which is needed for reaction. However, even these systems are limited by the thermal mass of the coolant and the insulating efficiency of the package and can only extend the time that the products can be stored or shipped without external refrigeration. In cases where the material does reach the necessary temperature for reaction and significant heat liberation, there is the possibility of thermal destruction of the outer shipping container. In order to alleviate such a problem, the U.S. Department of Transportation currently requires that exothermic type materials must be shipped in special temperature controlled environments. This requirement is imposed because of the potential for the coolant to completely dissipate over time due to the insulating inefficiency of the outer package. This causes heat release from the exothermic material and destruction of the outer package. Currently, exothermic materials cannot be transported by air because of the potential for "self-heating" to excessively high temperatures and ground transport is limited to shipment in special temperature controlled containers.
The prior art discloses many different shipping and packaging systems using heat sink materials and other coolant and temperature control means. For example, U.S. Pat. No. 5,355,684 issued Oct. 18, 1994 to W. Guice, discloses a system for the storage and shipment of frozen and chilled biological materials consisting of a cryogenically insulated vessel containing a heat sink material. U.S. Pat. No. 4,903,493 issued Feb. 27, 1990 to W. Van Iperen et al. discloses the use of heat sink materials for protecting thermolabile goods such as thermometers. U.S. Pat. No. 4,530,816 issued Jul. 23, 1985 to D. Douglas discloses a method and apparatus for cooling, preserving and safely transporting biological materials using a container with cooling and thermal insulating means.
The prior art, exemplified above, has disclosed many different shipping and packaging systems with cooling and other protective means. These shipping and packaging systems are used to preserve the materials being shipped by temporarily mitigating the affect of heat entering from outside the package. However, the difficulty of handling exothermic materials and the underlying problem of additional and significant heat liberation inside the package has not been dealt with.
Accordingly, the object and purpose of this invention is to provide a safe shipping and storage system for exothermic materials where the risk of reaching unacceptably high temperatures during shipping and storage is alleviated or significantly mitigated.